Synthesis of polyamine-bridged polysilsesquioxanes and their adsorption properties for heavy metal ions

Four types of polyamine-bridged polysilsesquioxane adsorbents were prepared via a facile sol-gel method using pre-synthesized ethanediamine (EDA)-and diethylenetriamine (DETA)-bridged monomers containing soft organic bridge. Infrared spectra (IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TG), elemental analysis, and nitrogen gas adsorption-desorption were used to characterize their structures. Porogen hexadecyl tyimethyl ammonium bromide (CTAB) was found to be efficient in increasing the porosity of the absorbents. Adsorption experiments at different temperatures showed that the obtained absorbents exhibited relatively high adsorption capacities for Hg(II). Pseudo second-order model is more suitable for describing the adsorption kinetics in the temperature range of 15-35 degrees C. Compared with Freundlich models, Langmuir isotherm was better to describe the adsorption process of Hg(II) for all adsorbents. Finally, the thermodynamic parameters demonstrated that the adsorption reaction was endothermic and spontaneous. (C) 2017 American Institute of Chemical Engineers